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- since 1996 -
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dessy ana laila sari
Student,
Brawijaya University, Indonesia, Joined Oct 2016, 5

dessy ana laila sari

Student,
Brawijaya University,
Indonesia,
Joined Oct 2016
5
10:18 Nov-21-2016
which one ?
zoom image



hello, i have question. i'm doing thickness measurement using angle beam probe. the output signal i got is on attached file here. for thickness measurement which signal is the right time for thickness time?

regards

 
 Reply 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1096

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1096
12:48 Nov-21-2016
Re: which one ?
In Reply to dessy ana laila sari at 10:18 Nov-21-2016 (Opening).

Dessy

This is not a familiar method of taking thickness measurements. Is there any motive behind not using a digital thickness meter or a conventional ultrasonic test machine with zero degree compression wave probe?

 
 Reply 
 
dessy ana laila sari
Student,
Brawijaya University, Indonesia, Joined Oct 2016, 5

dessy ana laila sari

Student,
Brawijaya University,
Indonesia,
Joined Oct 2016
5
12:56 Nov-21-2016
Re: which one ?
In Reply to Nigel Armstrong at 12:48 Nov-21-2016 .

this method for my thesis. i want to measure some plate thickness using angle probe. what should i do? i'm confused with which signal time i should use.

regards

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1286

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1286
13:46 Nov-21-2016
Re: which one ?
In Reply to dessy ana laila sari at 12:56 Nov-21-2016 .

I suggest that the long line of arrival times from a pulse-echo plane wave is not appropriate for your task. Perhaps you might like to try using a pitch-catch arrangement and use Pythagoras on the peaked received signal . There can still be some error due to the lamda/d effects but at least you will have a single signal to deal with.

 
 Reply 
 
James Scalf
NDT Inspector,
Global Integrity, Canada, Joined Oct 2012, 274

James Scalf

NDT Inspector,
Global Integrity,
Canada,
Joined Oct 2012
274
13:59 Nov-21-2016
Re: which one ?
In Reply to dessy ana laila sari at 12:56 Nov-21-2016 .

Dessy,

What are you using for a reflector? I have done some work where I had no choice but to use an angled compression wave to determine a relative thickness. From the signal response above it looks to me like you are using a "Corner Trap" which is not an ideal reflector for this kind of measurement. The reason I think this is you have two signals and what is probably happening is that the beam spread of the sound wave is causing some of the signals reflecting of the side walls to affect the central primary beam. When this occurs you can have your primary sound beam path distorted (slowed down for all intents) this can creates a double pulse representation on the screen display much like what you are seeing. Try changing your pulse repetition frequency. Sometimes there is a distinct pulse duration and frequency that will eliminate this effect. Also try using, if it is possible for your application, a circumferential (round) reflector. These are not angle dependant and have no side walls to allow for a disruptive wave front.

As I said this may not be the solution to your particular problem but having trialed similar situations the above solved the issues I was having. Hope this helps. Cheers...

James

 
 Reply 
 
dessy ana laila sari
Student,
Brawijaya University, Indonesia, Joined Oct 2016, 5

dessy ana laila sari

Student,
Brawijaya University,
Indonesia,
Joined Oct 2016
5
06:19 Nov-22-2016
Re: which one ?
In Reply to Ed Ginzel at 13:46 Nov-21-2016 .

hello,

i'm already using the pitch-catch method. and the signal is like that

what should i do?

regards

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1286

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1286
13:47 Nov-22-2016
Re: which one ?
In Reply to dessy ana laila sari at 06:19 Nov-22-2016 .

Dessy, you have provided almost no information about the setup. We have no idea what the probes are, what the coupling technique is, what the material is that is being assessed, what the test piece geometry is, etc. Even the fact that it is in pitch-catch was only discovered after your third posting. It sounds like this is a school project and if it is a "thesis" you probably would have a solid foundation in the mechanical setup requirements from your undergrad studies. You might speed up the process by asking your thesis supervisor (or making a useful disclosure on the forum postings).
The signal you provided is almost meaningless. It is a TINY response peaking at 2mV and the background noise is significant. The signals rise at about 15µs and last until about 28µs. The times are rather large and the amplitudes rather small but all together they mean nothing to anyone looking at just the voltage responses.

 
 Reply 
 

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